For this project, we are now focusing on the idiopathic inflammatory myopathies (IIM), also known as the myositis syndromes, as prototypic autoimmune diseases from which principles learned in these disorders may be applied generally to other diseases. The myositis syndromes are associated with substantial lifelong morbidity and mortality. Their treatment is unsatisfactory in many cases and drug efficacy evaluation is hampered by the lack of reliable and standardized measures of disease outcome. No agents are currently licensed for the treatment of IIM and few have been studied in randomized controlled clinical trials. Because of the lack of consensus on how to best measure disease in the myositis syndromes, and to enhance recruitment of patients for other studies, new disease assessment tools are being developed and validated to apply to all forms of myositis in both adults and children. We have organized a multidisciplinary collaborative group of over 300 adult and pediatric specialists with special interest in myositis, known as the International Myositis Assessment and Clinical Studies Group (IMACS) to assist in this project. The goals of IMACS are to standardize the conduct and reporting of clinical studies in all forms of IIM. Achieving these goals should enhance the consistency by which clinical trials are performed, improve the capacity to compare different treatments, and encourage development of promising novel therapeutic agents. Therapeutic studies of novel biologic agents are in progress and others are being planned to utilize these outcome measures in prospective trials. Together, and with input from the FDA and the European regulatory bodies, and with collaboration with Pediatric Rheumatology International Trials Organization (PRINTO), IMACS has: 1) developed and validated new tools to assess myositis disease activity and damage; 2) achieved consensus on core set outcome measures to comprehensively describe disease activity; 3) delineated preliminary and recently ACR-EULAR approved definitions of improvement for use as clinical trial outcomes, which provide clinically meaningful change in combinations of the core set measures in a composite endpoint; 4) developed international consensus guidelines on details of the conduct of multi-center therapeutic trials for adult and juvenile IIM; 5) developed a clinical trial and outcomes data repository to allow us to reassess and revise IMACS tools; and 6) developed new outcome measures for polymyositis and dermatomyositis in adults and children that should result in more sensitive evaluations and fewer subjects needed for future clinical trials. We have created a website to consolidate all IMACS activities, including member lists and contacts, educational materials, meeting presentations, references, assessment tools and ongoing and future collaborative initiatives and studies (https://www.niehs.nih.gov/research/resources/imacs/index.cfm). The therapy of myositis is focused on immunosuppression to minimize effects from immune activation and rehabilitation to improve remaining muscle function. Given the poor outcomes of myositis patients with standard therapy, novel biologic anti-inflammatory agents, which have been shown to be safe and effective for other immune-mediated diseases and have rationale for use in myositis, are reasonable candidates for study and may represent important advances in the treatment of myositis in the future. Our experience is that conducting therapeutic trials also greatly enhances recruitment to our epidemiologic investigations. We are taking advantage of the rituximab in myositis trial to identify changes in gene expression patterns in muscle, skin and peripheral blood and the imaging features and immunopathology of muscle, skin and peripheral cells before (week 0) and after (week 16) therapy. These will also be correlated with the large number of clinical, laboratory and research variables already planned to be collected in the core RIM study. Furthermore, knowing specifically which gene expression patterns are altered in resistant patients before rituximab, and which are changed after rituximab therapy -- in conjunction with flow cytometry of peripheral cells and immunopathology of the tissues -- will help in understanding more about the pathogenesis of myositis and the possible contribution of B lymphocytes and their subsets. The identification of environmental risk factors for autoimmune diseases offers the hope of preventing some of these disorders by exposure avoidance in genetically susceptible individuals. Investigations underway in our companion study ES101074, Environmental/genetic Risk Factors and Pathogenesis of Autoimmune Disease, which is focused on identifying environmental risk factors for autoimmune conditions, may offer approaches to disease prevention. Exposures that are known to be important in inducing disease exacerbations in established disease may be triggers for disease onset as well. One example is our recent finding that ultraviolet radiation, known to induce exacerbations of lupus and dermatomyositis, likely plays an important role in the development of dermatomyositis and related autoantibodies as well as flares of disease. Studies to assess the efficacy of exposure avoidance in reducing myositis disease flares should be benefited from the validated outcome measures we are developing.